Q Dear Practical Poultry, I am having problems with my seven to eight week-old chickens. They have swollen/enlarged hocks with distorted leg movement. They are fed on chick starter crumbs and the breeds concerned are Rhode Island Red and Light Sussex.

A Rhode Island Reds and Light Sussex are both heavy breeds and, as pure breeds, would normally be quite slow growers as opposed to crossbreds. If these breeds (as with any pure breed bird) are fed too richly they grow too quickly and body weight increases too rapidly for the weight bearing capabilities of the legs. Hock problems commonly result. Chick crumbs should really only be fed for the first month, then the feed slowly changed to a grower pellet and/or grain.
Another possible factor may be the length of time these birds are under a heat lamp as this will also force the growth. Chicks generally should be off the lamp completely after five weeks. This is not an exact time but depends on the outside temperature. The heat must be removed in stages, lifting the light higher to get less heat at floor level, or by changing to an electric hen from about three weeks old, then turning the heat off in the day and leaving it on at night for a week or so before turning if off altogether.
As stated above, there are other reasons for swollen joints - infection (Mycoplasma synoviae, for example) and trauma; this one being unlikely as several birds are affected. Infection would initially cause a fluidly swollen joint, with other joints also affected in some birds and maybe a slight respiratory infection if Mycoplasma is involved. I would start by altering the feeding regime and slowing the growth of these birds and subsequent batches. Should other signs arise then infection should be considered.